In an integrated limiting amplifier (LA), a large resistance/capacitance (RC) low-pass filter is typically utilized to sense and extract the LA's direct current (DC) offset. The DC offset may have one or more contributions including an intrinsic DC offset that arises due to mismatches in the dimensions or doping characteristics of the LA's constituent transistors, among other possibilities. The output of the filter—the DC offset—is fed back to the LA's input stage in negative feedback to cancel or compensate for the DC offset. Typically, industry specifications dictate that the time constant of the filter be very large (e.g., in the tens of kilohertz (kHz)) such that the low-frequency cutoff of the LA is sufficiently low so that the LA can tolerate long strings of consecutive identical digits (CIDs) without introducing baseline wander (also referred to as “DC drift”) into the LA output signal. Consequently, the filter capacitance (C) must be large, often in the microfarad range. Achieving such a large capacitance on-chip would require a very large chip (e.g., silicon chip) area. Such a required area is expensive and often unfeasible.
Thus, to produce the large required capacitance in a smaller and achievable silicon chip area, the filter's capacitor is often enclosed in a negative feedback loop to increase the effective capacitance of the filter, a well-known technique referred to as the Miller effect. The feedback loop, also referred to as the “Miller loop,” generally comprises one or more voltage amplifiers (referred to collectively as the “Miller amplifier”). Specifically, using the Miller amplifier, the capacitance of the filter may be increased by a factor of 1+AV, where AV is the total voltage gain of the Miller amplifier. The amplifiers of the Miller loop (i.e., the Miller amplifier) should remain in their linear operating regions in order to realize the desired capacitance amplification. If the amplifiers become non-linear, the gain AV decreases, and consequently so too does the amplified capacitance of the filter.